Bottom Line:
Three-dimensional (3D) visualization technique was applied to show the delineation results.The time required to generate the CTV was greatly reduced.Moreover, this new method improved inter- and intra-observer variability in defining the CTV.

Objects: To introduce a new method for generating the clinical target volume (CTV) from gross tumor volume (GTV) using the geodesic distance calculation for glioma.

Methods: One glioblastoma patient was enrolled. The GTV and natural barriers were contoured on each slice of the computer tomography (CT) simulation images. Then, a graphic processing unit based on a parallel Euclidean distance transform was used to generate the CTV considering natural barriers. Three-dimensional (3D) visualization technique was applied to show the delineation results. Speed of operation and precision were compared between this new delineation method and the traditional method.

Results: In considering spatial barriers, the shortest distance from the point sheltered from these barriers equals the sum of the distance along the shortest path between the two points; this consists of several segments and evades the spatial barriers, rather than being the direct Euclidean distance between two points. The CTV was generated irregularly rather than as a spherical shape. The time required to generate the CTV was greatly reduced. Moreover, this new method improved inter- and intra-observer variability in defining the CTV.

Conclusions: Compared with the traditional CTV delineation, this new method using geodesic distance calculation not only greatly shortens the time to modify the CTV, but also has better reproducibility.

Mentions:
After the 3D Voronoi diagram had been obtained and the spatial octree for the barriers constructed, we obtained the final target volume by calculation of the multiple iterative growths. First, the CTV was generated using the default external diffusion value (i.e. the growth radius, d) based on the GTV. In the first growth iteration, the system calculated the shortest distance in space from the GTV for each point based on the 3D Voronoi diagram to attain the corresponding segment L. If the distance was longer than d, the corresponding point was removed from the growth target volume. If the distance was shorter than d, it was necessary to judge if the segment L intersected with the barriers. If the segment L intersected with the barriers, the point was similarly removed from the target volume. The green area in Figure 2 represents the results that were obtained. For each point in space, if ds was denoted as the cumulative shortest distance between the point and the GTV, then ds for each point in the target volume was the shortest Euclidean distance away from the GTV in the first growth iteration.

Mentions:
After the 3D Voronoi diagram had been obtained and the spatial octree for the barriers constructed, we obtained the final target volume by calculation of the multiple iterative growths. First, the CTV was generated using the default external diffusion value (i.e. the growth radius, d) based on the GTV. In the first growth iteration, the system calculated the shortest distance in space from the GTV for each point based on the 3D Voronoi diagram to attain the corresponding segment L. If the distance was longer than d, the corresponding point was removed from the growth target volume. If the distance was shorter than d, it was necessary to judge if the segment L intersected with the barriers. If the segment L intersected with the barriers, the point was similarly removed from the target volume. The green area in Figure 2 represents the results that were obtained. For each point in space, if ds was denoted as the cumulative shortest distance between the point and the GTV, then ds for each point in the target volume was the shortest Euclidean distance away from the GTV in the first growth iteration.

Bottom Line:
Three-dimensional (3D) visualization technique was applied to show the delineation results.The time required to generate the CTV was greatly reduced.Moreover, this new method improved inter- and intra-observer variability in defining the CTV.

Objects: To introduce a new method for generating the clinical target volume (CTV) from gross tumor volume (GTV) using the geodesic distance calculation for glioma.

Methods: One glioblastoma patient was enrolled. The GTV and natural barriers were contoured on each slice of the computer tomography (CT) simulation images. Then, a graphic processing unit based on a parallel Euclidean distance transform was used to generate the CTV considering natural barriers. Three-dimensional (3D) visualization technique was applied to show the delineation results. Speed of operation and precision were compared between this new delineation method and the traditional method.

Results: In considering spatial barriers, the shortest distance from the point sheltered from these barriers equals the sum of the distance along the shortest path between the two points; this consists of several segments and evades the spatial barriers, rather than being the direct Euclidean distance between two points. The CTV was generated irregularly rather than as a spherical shape. The time required to generate the CTV was greatly reduced. Moreover, this new method improved inter- and intra-observer variability in defining the CTV.

Conclusions: Compared with the traditional CTV delineation, this new method using geodesic distance calculation not only greatly shortens the time to modify the CTV, but also has better reproducibility.